Basic Usage

.. function:: dump(obj, fp, skipkeys=False, ensure_ascii=True, \
                   check_circular=True, allow_nan=True, cls=None, \
                   indent=None, separators=None, encoding="utf-8", \
                   default=None, sort_keys=False, **kw)

   Serialize *obj* as a JSON formatted stream to *fp* (a ``.write()``-supporting
   :term:`file-like object`) using this :ref:`conversion table
   <py-to-json-table>`.

   If *skipkeys* is ``True`` (default: ``False``), then dict keys that are not
   of a basic type (:class:`str`, :class:`unicode`, :class:`int`, :class:`long`,
   :class:`float`, :class:`bool`, ``None``) will be skipped instead of raising a
   :exc:`TypeError`.

   If *ensure_ascii* is ``True`` (the default), all non-ASCII characters in the
   output are escaped with ``\uXXXX`` sequences, and the result is a
   :class:`str` instance consisting of ASCII characters only.  If
   *ensure_ascii* is ``False``, some chunks written to *fp* may be
   :class:`unicode` instances.  This usually happens because the input contains
   unicode strings or the *encoding* parameter is used.  Unless ``fp.write()``
   explicitly understands :class:`unicode` (as in :func:`codecs.getwriter`)
   this is likely to cause an error.

   If *check_circular* is ``False`` (default: ``True``), then the circular
   reference check for container types will be skipped and a circular reference
   will result in an :exc:`OverflowError` (or worse).

   If *allow_nan* is ``False`` (default: ``True``), then it will be a
   :exc:`ValueError` to serialize out of range :class:`float` values (``nan``,
   ``inf``, ``-inf``) in strict compliance of the JSON specification, instead of
   using the JavaScript equivalents (``NaN``, ``Infinity``, ``-Infinity``).

   If *indent* is a non-negative integer, then JSON array elements and object
   members will be pretty-printed with that indent level.  An indent level of 0,
   or negative, will only insert newlines.  ``None`` (the default) selects the
   most compact representation.

   .. note::

      Since the default item separator is ``', '``,  the output might include
      trailing whitespace when *indent* is specified.  You can use
      ``separators=(',', ': ')`` to avoid this.

   If *separators* is an ``(item_separator, dict_separator)`` tuple, then it
   will be used instead of the default ``(', ', ': ')`` separators.  ``(',',
   ':')`` is the most compact JSON representation.

   *encoding* is the character encoding for str instances, default is UTF-8.

   *default(obj)* is a function that should return a serializable version of
   *obj* or raise :exc:`TypeError`.  The default simply raises :exc:`TypeError`.

   If *sort_keys* is ``True`` (default: ``False``), then the output of
   dictionaries will be sorted by key.

   To use a custom :class:`JSONEncoder` subclass (e.g. one that overrides the
   :meth:`default` method to serialize additional types), specify it with the
   *cls* kwarg; otherwise :class:`JSONEncoder` is used.

   .. note::

      Unlike :mod:`pickle` and :mod:`marshal`, JSON is not a framed protocol so
      trying to serialize more objects with repeated calls to :func:`dump` and
      the same *fp* will result in an invalid JSON file.

.. function:: dumps(obj, skipkeys=False, ensure_ascii=True, \
                    check_circular=True, allow_nan=True, cls=None, \
                    indent=None, separators=None, encoding="utf-8", \
                    default=None, sort_keys=False, **kw)

   Serialize *obj* to a JSON formatted :class:`str` using this :ref:`conversion
   table <py-to-json-table>`.  If *ensure_ascii* is ``False``, the result may
   contain non-ASCII characters and the return value may be a :class:`unicode`
   instance.

   The arguments have the same meaning as in :func:`dump`.

   .. note::

      Keys in key/value pairs of JSON are always of the type :class:`str`. When
      a dictionary is converted into JSON, all the keys of the dictionary are
      coerced to strings. As a result of this, if a dictionary is converted
      into JSON and then back into a dictionary, the dictionary may not equal
      the original one. That is, ``loads(dumps(x)) != x`` if x has non-string
      keys.

.. function:: load(fp[, encoding[, cls[, object_hook[, parse_float[, parse_int[, parse_constant[, object_pairs_hook[, **kw]]]]]]]])

   Deserialize *fp* (a ``.read()``-supporting :term:`file-like object`
   containing a JSON document) to a Python object using this :ref:`conversion
   table <json-to-py-table>`.

   If the contents of *fp* are encoded with an ASCII based encoding other than
   UTF-8 (e.g. latin-1), then an appropriate *encoding* name must be specified.
   Encodings that are not ASCII based (such as UCS-2) are not allowed, and
   should be wrapped with ``codecs.getreader(encoding)(fp)``, or simply decoded
   to a :class:`unicode` object and passed to :func:`loads`.

   *object_hook* is an optional function that will be called with the result of
   any object literal decoded (a :class:`dict`).  The return value of
   *object_hook* will be used instead of the :class:`dict`.  This feature can be used
   to implement custom decoders (e.g. `JSON-RPC <http://www.jsonrpc.org>`_
   class hinting).

   *object_pairs_hook* is an optional function that will be called with the
   result of any object literal decoded with an ordered list of pairs.  The
   return value of *object_pairs_hook* will be used instead of the
   :class:`dict`.  This feature can be used to implement custom decoders that
   rely on the order that the key and value pairs are decoded (for example,
   :func:`collections.OrderedDict` will remember the order of insertion). If
   *object_hook* is also defined, the *object_pairs_hook* takes priority.

   .. versionchanged:: 2.7
      Added support for *object_pairs_hook*.

   *parse_float*, if specified, will be called with the string of every JSON
   float to be decoded.  By default, this is equivalent to ``float(num_str)``.
   This can be used to use another datatype or parser for JSON floats
   (e.g. :class:`decimal.Decimal`).

   *parse_int*, if specified, will be called with the string of every JSON int
   to be decoded.  By default, this is equivalent to ``int(num_str)``.  This can
   be used to use another datatype or parser for JSON integers
   (e.g. :class:`float`).

   *parse_constant*, if specified, will be called with one of the following
   strings: ``'-Infinity'``, ``'Infinity'``, ``'NaN'``.
   This can be used to raise an exception if invalid JSON numbers
   are encountered.

   .. versionchanged:: 2.7
      *parse_constant* doesn't get called on 'null', 'true', 'false' anymore.

   To use a custom :class:`JSONDecoder` subclass, specify it with the ``cls``
   kwarg; otherwise :class:`JSONDecoder` is used.  Additional keyword arguments
   will be passed to the constructor of the class.

.. function:: loads(s[, encoding[, cls[, object_hook[, parse_float[, parse_int[, parse_constant[, object_pairs_hook[, **kw]]]]]]]])

   Deserialize *s* (a :class:`str` or :class:`unicode` instance containing a JSON
   document) to a Python object using this :ref:`conversion table
   <json-to-py-table>`.

   If *s* is a :class:`str` instance and is encoded with an ASCII based encoding
   other than UTF-8 (e.g. latin-1), then an appropriate *encoding* name must be
   specified.  Encodings that are not ASCII based (such as UCS-2) are not
   allowed and should be decoded to :class:`unicode` first.

   The other arguments have the same meaning as in :func:`load`.

Encoders and Decoders

Simple JSON decoder.

Performs the following translations in decoding by default:

It also understands NaN, Infinity, and -Infinity as their corresponding float values, which is outside the JSON spec.

encoding determines the encoding used to interpret any :class:`str` objects decoded by this instance (UTF-8 by default). It has no effect when decoding :class:`unicode` objects.

Note that currently only encodings that are a superset of ASCII work, strings of other encodings should be passed in as :class:`unicode`.

object_hook, if specified, will be called with the result of every JSON object decoded and its return value will be used in place of the given :class:`dict`. This can be used to provide custom deserializations (e.g. to support JSON-RPC class hinting).

object_pairs_hook, if specified will be called with the result of every JSON object decoded with an ordered list of pairs. The return value of object_pairs_hook will be used instead of the :class:`dict`. This feature can be used to implement custom decoders that rely on the order that the key and value pairs are decoded (for example, :func:`collections.OrderedDict` will remember the order of insertion). If object_hook is also defined, the object_pairs_hook takes priority.

.. versionchanged:: 2.7
   Added support for *object_pairs_hook*.

parse_float, if specified, will be called with the string of every JSON float to be decoded. By default, this is equivalent to float(num_str). This can be used to use another datatype or parser for JSON floats (e.g. :class:`decimal.Decimal`).

parse_int, if specified, will be called with the string of every JSON int to be decoded. By default, this is equivalent to int(num_str). This can be used to use another datatype or parser for JSON integers (e.g. :class:`float`).

parse_constant, if specified, will be called with one of the following strings: '-Infinity', 'Infinity', 'NaN', 'null', 'true', 'false'. This can be used to raise an exception if invalid JSON numbers are encountered.

If strict is False (True is the default), then control characters will be allowed inside strings. Control characters in this context are those with character codes in the 0-31 range, including '\t' (tab), '\n', '\r' and '\0'.

If the data being deserialized is not a valid JSON document, a :exc:`ValueError` will be raised.

.. method:: decode(s)

   Return the Python representation of *s* (a :class:`str` or
   :class:`unicode` instance containing a JSON document)

.. method:: raw_decode(s)

   Decode a JSON document from *s* (a :class:`str` or :class:`unicode`
   beginning with a JSON document) and return a 2-tuple of the Python
   representation and the index in *s* where the document ended.

   This can be used to decode a JSON document from a string that may have
   extraneous data at the end.

Extensible JSON encoder for Python data structures.

Supports the following objects and types by default:

To extend this to recognize other objects, subclass and implement a :meth:`default` method with another method that returns a serializable object for o if possible, otherwise it should call the superclass implementation (to raise :exc:`TypeError`).

If skipkeys is False (the default), then it is a :exc:`TypeError` to attempt encoding of keys that are not str, int, long, float or None. If skipkeys is True, such items are simply skipped.

If ensure_ascii is True (the default), all non-ASCII characters in the output are escaped with \uXXXX sequences, and the results are :class:`str` instances consisting of ASCII characters only. If ensure_ascii is False, a result may be a :class:`unicode` instance. This usually happens if the input contains unicode strings or the encoding parameter is used.

If check_circular is True (the default), then lists, dicts, and custom encoded objects will be checked for circular references during encoding to prevent an infinite recursion (which would cause an :exc:`OverflowError`). Otherwise, no such check takes place.

If allow_nan is True (the default), then NaN, Infinity, and -Infinity will be encoded as such. This behavior is not JSON specification compliant, but is consistent with most JavaScript based encoders and decoders. Otherwise, it will be a :exc:`ValueError` to encode such floats.

If sort_keys is True (default False), then the output of dictionaries will be sorted by key; this is useful for regression tests to ensure that JSON serializations can be compared on a day-to-day basis.

If indent is a non-negative integer (it is None by default), then JSON array elements and object members will be pretty-printed with that indent level. An indent level of 0 will only insert newlines. None is the most compact representation.

If specified, separators should be an (item_separator, key_separator) tuple. The default is (', ', ': '). To get the most compact JSON representation, you should specify (',', ':') to eliminate whitespace.

If specified, default is a function that gets called for objects that can't otherwise be serialized. It should return a JSON encodable version of the object or raise a :exc:`TypeError`.

If encoding is not None, then all input strings will be transformed into unicode using that encoding prior to JSON-encoding. The default is UTF-8.

.. method:: default(o)

   Implement this method in a subclass such that it returns a serializable
   object for *o*, or calls the base implementation (to raise a
   :exc:`TypeError`).

   For example, to support arbitrary iterators, you could implement default
   like this::

      def default(self, o):
         try:
             iterable = iter(o)
         except TypeError:
             pass
         else:
             return list(iterable)
         # Let the base class default method raise the TypeError
         return JSONEncoder.default(self, o)

.. method:: encode(o)

   Return a JSON string representation of a Python data structure, *o*.  For
   example::

     >>> JSONEncoder().encode({"foo": ["bar", "baz"]})
     '{"foo": ["bar", "baz"]}'

.. method:: iterencode(o)

   Encode the given object, *o*, and yield each string representation as
   available.  For example::

         for chunk in JSONEncoder().iterencode(bigobject):
             mysocket.write(chunk)

Standard Compliance

The JSON format is specified by RFC 4627. This section details this module's level of compliance with the RFC. For simplicity, :class:`JSONEncoder` and :class:`JSONDecoder` subclasses, and parameters other than those explicitly mentioned, are not considered.

This module does not comply with the RFC in a strict fashion, implementing some extensions that are valid JavaScript but not valid JSON. In particular:

• Top-level non-object, non-array values are accepted and output;
• Infinite and NaN number values are accepted and output;
• Repeated names within an object are accepted, and only the value of the last name-value pair is used.

Since the RFC permits RFC-compliant parsers to accept input texts that are not RFC-compliant, this module's deserializer is technically RFC-compliant under default settings.

>>> just_a_json_string = '"spam and eggs"'  # Not by itself a valid JSON text
>>> json.loads(just_a_json_string)
u'spam and eggs'

>>> neither_a_list_nor_a_dict = u"spam and eggs"
>>> json.dumps(neither_a_list_nor_a_dict)  # The result is not a valid JSON text
'"spam and eggs"'

>>> # Neither of these calls raises an exception, but the results are not valid JSON
>>> json.dumps(float('-inf'))
'-Infinity'
>>> json.dumps(float('nan'))
'NaN'
>>> # Same when deserializing
>>> json.loads('-Infinity')
-inf
>>> json.loads('NaN')
nan

>>> weird_json = '{"x": 1, "x": 2, "x": 3}'
>>> json.loads(weird_json)
{u'x': 3}